Single vs doublr trailing @:s?

[Syntas_error]

I apologize if this question is very basic, but I, haven't been able to find a straightforward answer.

What's the difference between using a trailing @ and a trailing @@?

Is the trailing @ temporary (lasts for one/two iterations) while the @@ is permanent (until theree are no more values in the row)?

[Astounding · Accepted solution]

The single @ is temporary, for the current iteration of the DATA step only.

The double is permanent.  The only way to get to the next line includes:

• Executing another INPUT statement that does not end with @@
• Attempting to read past the end of the line, with neither TRUNCOVER nor MISSOVER in effect

[Tom]

Why not play with it and see what happens?

data test1;
  interation+1;
  do col=1 to 3 ;
    input x @;
    output;
  end;
cards;
1 2 3 4 5 6 
7 8 9 10 11 12
;

proc print;
run;

data test2;
  interation+1;
  do col=1 to 3 ;
    input x @@;
    output;
  end;
cards;
1 2 3 4 5 6 
7 8 9 10 11 12
; 

proc print;
run;

[AndrewHowell]

A SINGLE trailing "@" holds the input buffer only for the current iteration of the data step (i.e, til processing returns to the top of the data step), or is passed a subsequent INPUT statement without a trailing "@".

A DOUBLE trailing "@" holds the input buffer indefinitely (i.e, multiple iterations of the data step) as long as there is data in the input buffer to read.

Hope that helps?